Recently, in the manufacture of semiconductors, a CMP (Chemical Mechanical Polishing) method is extensively used to flatten an insulator film, a metal film, or a polycrystalline silicon film formed with the intention of filling grooves on each substrate surface. The CMP method is a method of supplying a polishing agent (slurry) containing abrasive grains and a chemical solution onto a polishing pad, and bringing workpieces into contact with the polishing pad to combine a chemical action of the chemical solution with a mechanical action of the abrasive grains, thereby flattening surfaces of the workpieces. According to this method, however, there is a problem that mechanical damage due to the abrasive grains cannot be avoided and polishing damage occurs on the surfaces of the workpieces.